Epstein-Barr virus is an orally transmitted herpesvirus that persistently infects nearly all humans by adulthood. Primary EBV infection is associated with vigorous lytic replication, as evidenced by viral shedding in oral secretions and robust serologic responses to many lytic proteins, and high numbers of latently infected B cells. However, it is unknown whether lytic replication is the primary mechanism for viral amplificationduring acute infection and whether [ytic replication is required for invasion of the peripheral blood where B cell infection is critical for establishing life, long persistent infection. These questions are difficult to address in humans since acute, primary infection is not usually recognized unless infectious mononucleosis develops, and this typically occurs weeks after oral virus inoculation and initial infection. We have developed a model for EBV infection using a closely related herpesvirus that naturally infects rhesus macaques and is in the same lymphocryptovirus (LCV) genus as EBV. The rhLCV genome sequence reveals an identical gene repertoire to EBV, and rhLCV infection has virtually identical biology to EBV infection. RhLCV naive rhesus macaques can be experimentally infected allowing access to the period immediately following oral inoculation. In the previous funding period, we have defined the parameters of acute infection after oral inoculation in both immunocompetent hosts and hosts immunosuppressed by co-infectionwith a chimeric human/simian immunodeficiency virus (SHIV). Of note, we showed that rhLCV infection can be associated with the development of B cell lymphomas and proliferative epithelial lesions similar to oral hairy leukoplakia in AIDS patients. In addition, we described the CD8+ T cell responses to lytic and latent rhLCV proteins. The development of this model system now allows us to address in detail the role of lytic viral replication during acute infection of immunocompetent and immunosuppressed hosts in the following specific aims: Specific Aim #1 - What is the role of viral replication in primary rhLCV infection after oral inoculation of immunocompetent rhesus macaques? Specific Aim #2 - What is the role of viral replication in primary rhLCV infection after oral inoculation of SHIV immunosuppressed rhesus macaques? Specific aim #3 - How early do CD8+ CTL specific for lytic proteins develop in acute rhLCV infection? These studies will elucidate the role of lytic viral replication and the immune response during acute infection that would otherwise be difficult, or impossible, to study in humans. A better understanding of the interplay between lytic EBV infection and the immune response to lytic EBV proteins will contribute to development of novel therapeutic approaches for control of EBV infection and diseases associated with lytic EBV replication, such as oral hairy leukoplakia.